When a central atom has an expanded octet, what geometric shape might the species exhibit?

See saw

Explanation:

An expanded octet shape best resembles the shape of a see saw. Generally in an expanded octet shape , the atom at the center of the structure has a Lewis structure that possess five or six regions of electron density. Thus there are can be more than one geometrical shape depending on the number of lone pairs. They have more that 8 electrons in their orbit and thus violate the octet rule.

Some common compounds that exhibits these expanded octet shape are Phosphorus pentachloride (PCl5) , hexafluoride (SF6)